libcpp: adjust pedwarn handling

Using cpp_pedwarning (CPP_W_PEDANTIC instead of if (CPP_PEDANTIC cpp_error
lets users suppress these diagnostics with
 #pragma GCC diagnostic ignored "-Wpedantic".

This patch changes all instances of the cpp_error (CPP_DL_PEDWARN to
cpp_pedwarning.  In cases where the extension appears in a later C++
revision, we now condition the warning on the relevant -Wc++??-extensions
flag instead of -Wpedantic; in such cases often the if (CPP_PEDANTIC) check
is retained to preserve the default non-warning behavior.

I didn't attempt to adjust the warning flags for the C compiler, since it
seems to follow a different system than C++.

The CPP_PEDANTIC check is also kept in _cpp_lex_direct to avoid an ICE in
the self-tests from cb.diagnostics not being initialized.

While working on testcases for these changes I noticed that the c-c++-common
tests are not run with -pedantic-errors by default like the gcc.dg and
g++.dg directories are.  And if I specify -pedantic-errors with dg-options,
the default -std= changes from c++?? to gnu++??, which interferes with some
other pedwarns.  So two of the tests are C++-only.

libcpp/ChangeLog:

	* include/cpplib.h (enum cpp_warning_reason): Add
	CPP_W_CXX{14,17,20,23}_EXTENSIONS.
	* charset.cc (_cpp_valid_ucn, convert_hex, convert_oct)
	(convert_escape, narrow_str_to_charconst): Use cpp_pedwarning
	instead of cpp_error for pedwarns.
	* directives.cc (directive_diagnostics, _cpp_handle_directive)
	(do_line, do_elif): Likewise.
	* expr.cc (cpp_classify_number, eval_token): Likewise.
	* lex.cc (skip_whitespace, maybe_va_opt_error)
	(_cpp_lex_direct): Likewise.
	* macro.cc (_cpp_arguments_ok): Likewise.
	(replace_args): Use -Wvariadic-macros for pedwarn about
	empty macro arguments.

gcc/c-family/ChangeLog:

	* c.opt: Add CppReason for Wc++{14,17,20,23}-extensions.
	* c-pragma.cc (handle_pragma_diagnostic_impl): Don't check
	OPT_Wc__23_extensions.

gcc/testsuite/ChangeLog:

	* c-c++-common/pragma-diag-17.c: New test.
	* g++.dg/cpp0x/va-opt1.C: New test.
	* g++.dg/cpp23/named-universal-char-escape3.C: New test.

1 files changed, 44 insertions, 34 deletions

diff --git a/libcpp/directives.cc b/libcpp/directives.cc
index f8d9898..859cd04 100644
--- a/libcpp/directives.cc
+++ b/libcpp/directives.cc
@@ -383,28 +383,37 @@ directive_diagnostics (cpp_reader *pfile, const directive *dir, int indented)
      -pedantic take precedence if both are applicable.  */
   if (! pfile->state.skipping)
     {
+      bool warned = false;
       if (dir->origin == EXTENSION
-	  && !(dir == &dtable[T_IMPORT] && CPP_OPTION (pfile, objc))
-	  && CPP_PEDANTIC (pfile))
-	cpp_error (pfile, CPP_DL_PEDWARN, "#%s is a GCC extension", dir->name);
-      else if (dir == &dtable[T_WARNING])
+	  && !(dir == &dtable[T_IMPORT] && CPP_OPTION (pfile, objc)))
+	warned
+	  = cpp_pedwarning (pfile, CPP_W_PEDANTIC, "#%s is a GCC extension",
+			    dir->name);
+      if (!warned && dir == &dtable[T_WARNING])
 	{
 	  if (CPP_PEDANTIC (pfile) && !CPP_OPTION (pfile, warning_directive))
 	    {
 	      if (CPP_OPTION (pfile, cplusplus))
-		cpp_error (pfile, CPP_DL_PEDWARN,
-			   "#%s before C++23 is a GCC extension", dir->name);
+		warned
+		  = cpp_pedwarning (pfile, CPP_W_CXX23_EXTENSIONS,
+				    "#%s before C++23 is a GCC extension",
+				    dir->name);
 	      else
-		cpp_error (pfile, CPP_DL_PEDWARN,
-			   "#%s before C23 is a GCC extension", dir->name);
+		warned
+		  = cpp_pedwarning (pfile, CPP_W_PEDANTIC,
+				    "#%s before C23 is a GCC extension",
+				    dir->name);
 	    }
-	  else if (CPP_OPTION (pfile, cpp_warn_c11_c23_compat) > 0)
-	    cpp_warning (pfile, CPP_W_C11_C23_COMPAT,
-			 "#%s before C23 is a GCC extension", dir->name);
+
+	  if (!warned && CPP_OPTION (pfile, cpp_warn_c11_c23_compat) > 0)
+	    warned = cpp_warning (pfile, CPP_W_C11_C23_COMPAT,
+				  "#%s before C23 is a GCC extension",
+				  dir->name);
 	}
-      else if (((dir->flags & DEPRECATED) != 0
-		|| (dir == &dtable[T_IMPORT] && !CPP_OPTION (pfile, objc)))
-	       && CPP_OPTION (pfile, cpp_warn_deprecated))
+
+      if (((dir->flags & DEPRECATED) != 0
+	   || (dir == &dtable[T_IMPORT] && !CPP_OPTION (pfile, objc)))
+	  && !warned)
 	cpp_warning (pfile, CPP_W_DEPRECATED,
                      "#%s is a deprecated GCC extension", dir->name);
     }
@@ -450,9 +459,9 @@ _cpp_handle_directive (cpp_reader *pfile, bool indented)
 
   if (was_parsing_args)
     {
-      if (CPP_OPTION (pfile, cpp_pedantic))
-	cpp_error (pfile, CPP_DL_PEDWARN,
-	     "embedding a directive within macro arguments is not portable");
+      cpp_pedwarning (pfile, CPP_W_PEDANTIC,
+		      "embedding a directive within macro arguments is not "
+		      "portable");
       pfile->state.parsing_args = 0;
       pfile->state.prevent_expansion = 0;
     }
@@ -477,10 +486,10 @@ _cpp_handle_directive (cpp_reader *pfile, bool indented)
   else if (dname->type == CPP_NUMBER && CPP_OPTION (pfile, lang) != CLK_ASM)
     {
       dir = &linemarker_dir;
-      if (CPP_PEDANTIC (pfile) && ! CPP_OPTION (pfile, preprocessed)
+      if (! CPP_OPTION (pfile, preprocessed)
 	  && ! pfile->state.skipping)
-	cpp_error (pfile, CPP_DL_PEDWARN,
-		   "style of line directive is a GCC extension");
+	cpp_pedwarning (pfile, CPP_W_PEDANTIC,
+			"style of line directive is a GCC extension");
     }
 
   if (dir)
@@ -1388,8 +1397,9 @@ do_line (cpp_reader *pfile)
       return;
     }
 
-  if (CPP_PEDANTIC (pfile) && (new_lineno == 0 || new_lineno > cap || wrapped))
-    cpp_error (pfile, CPP_DL_PEDWARN, "line number out of range");
+  if ((new_lineno == 0 || new_lineno > cap || wrapped)
+      && cpp_pedwarning (pfile, CPP_W_PEDANTIC, "line number out of range"))
+    ;
   else if (wrapped)
     cpp_error (pfile, CPP_DL_WARNING, "line number out of range");
 
@@ -2531,13 +2541,13 @@ do_elif (cpp_reader *pfile)
 	      && !pfile->state.skipping)
 	    {
 	      if (CPP_OPTION (pfile, cplusplus))
-		cpp_error (pfile, CPP_DL_PEDWARN,
-			   "#%s before C++23 is a GCC extension",
-			   pfile->directive->name);
+		cpp_pedwarning (pfile, CPP_W_CXX23_EXTENSIONS,
+				"#%s before C++23 is a GCC extension",
+				pfile->directive->name);
 	      else
-		cpp_error (pfile, CPP_DL_PEDWARN,
-			   "#%s before C23 is a GCC extension",
-			   pfile->directive->name);
+		cpp_pedwarning (pfile, CPP_W_PEDANTIC,
+				"#%s before C23 is a GCC extension",
+				pfile->directive->name);
 	    }
 	  pfile->state.skipping = 1;
 	}
@@ -2570,13 +2580,13 @@ do_elif (cpp_reader *pfile)
 		      && pfile->state.skipping != skip)
 		    {
 		      if (CPP_OPTION (pfile, cplusplus))
-			cpp_error (pfile, CPP_DL_PEDWARN,
-				   "#%s before C++23 is a GCC extension",
-				   pfile->directive->name);
+			cpp_pedwarning (pfile, CPP_W_CXX23_EXTENSIONS,
+					"#%s before C++23 is a GCC extension",
+					pfile->directive->name);
 		      else
-			cpp_error (pfile, CPP_DL_PEDWARN,
-				   "#%s before C23 is a GCC extension",
-				   pfile->directive->name);
+			cpp_pedwarning (pfile, CPP_W_PEDANTIC,
+					"#%s before C23 is a GCC extension",
+					pfile->directive->name);
 		    }
 		  pfile->state.skipping = skip;
 		}